The present disclosure relates to current mirrors, control methods, and image sensors and, more specifically, to a current mirror, a control method, and an image sensor with which any influence of the spatial distribution of GND (ground) potential or power supply potential may be reduced.
In a current mirror, a mirror current flows in a load transistor to which a current is mirrored. The mirror current is proportional to a reference current that flows in a driver transistor from which a current is mirrored. A ratio between the reference current and the mirror current is referred to as mirror ratio.
For a current mirror with an extremely high mirror ratio, e.g., a large-load current mirror, what is important is to enhance the driving capability of the driver transistor, i.e., to reduce the output impedance of the driver transistor. For reducing the output impedance of the driver transistor, an effective method is to configure the current mirror with FETs (Field Effect Transistors), and to configure the driver transistor as an SF (Source Follower) transistor.
The SF current mirror is described in Japanese Patent Application Laid-Open Publication No. Hei 3-159410, for example.